Field of the Invention
The present invention relates to a positive photosensitive resin composition using a silicone-skeleton-containing polymer compound, a photo-curable dry film formed by the positive photosensitive resin composition and a method for producing the same, patterning processes using the positive photosensitive resin composition or the photo-curable dry film, and a laminate obtained by laminating the photo-curable dry film on a substrate.
Description of the Related Art
As various electronic devices including a personal computer, a digital camera, and a mobile phone progress toward downsizing and higher performance, requirements are rapidly increasing for further downsizing, thinning, and densifying in semiconductor devices. Accordingly, it is desired to develop a photosensitive insulating material that can accommodate not only an increase in surface area of a substrate for the sake of higher productivity, but also a structure having fine concavity and convexity with high aspect ratio on a substrate, in high density mounting technologies including a chip size package or a chip scale package (CSP) and a three-dimensional lamination.
As the photosensitive insulating material, there has been proposed a photo-curable resin composition that can be applied with a wide range of film thickness by a spin coating method, which is commonly used in the semiconductor device fabrication, can be processed into a fine pattern with a wide range of wavelength, and can be post-cured at low temperature to form a top coat having excellent flexibility, heat resistance, electric characteristics, adhesiveness, reliability, and chemical resistance to protect electric and electronic parts (Patent Document 1). The spin coating method has an advantage of easily forming a film on a substrate.
The photo-curable resin composition for providing a top coat to protect electric and electronic parts is used with a film thickness of 1 to 100 μm on a substrate. Unfortunately, the photo-curable resin composition has a practical limit of forming a film on a substrate by the spin coating method due to an increase in viscosity when the film thickness exceeds 30 μm.
Additionally, when the photo-curable resin composition is applied onto a substrate having an uneven surface by the spin coating method, the composition is difficult to coat the substrate uniformly. This easily causes voids in the photo-curable resin layer on an uneven portion of the substrate. It would therefore be desirable to improve planarity and step coverage. As an alternative coating method of the spin coating method, a spray coating method has been proposed (Patent Document 2). However, in principle, this method easily causes defects such as height difference due to unevenness of a substrate, film loss at pattern edge, and a pinhole in a recess bottom. Thus, the problems of planarity and step coverage still remain unsolved.
The recent high density mounting technology including a chip size package or a chip scale package (CSP) and a three-dimensional lamination has greatly expanded its emphasis in a technology that allows one to form a fine pattern having a high aspect ratio on a substrate and cover the pattern with metal such as copper for rewiring from a chip. As the chip advances toward higher density and higher integration, it is strongly desired in the rewiring technology to reduce the line width of the pattern and the size of a contact hole for connection between substrates. To obtain a fine pattern, lithography is commonly used. Above all, a negative photosensitive resin composition is suitable to obtain a fine pattern. The pattern used for rewiring is curable and permanently exists between chips or device chips, and is required to function as a top coat excellent in flexibility, heat resistance, electric characteristics, adhesiveness, reliability, and chemical resistance to protect electric and electronic parts. Thus, the resist composition for providing the pattern is preferably of a negative type.
However, if the negative photosensitive resin composition is used to form a contact hole for connecting substrates, wirings, or circuits in the three-dimensional lamination as a through electrode, the contact hole tends to be formed in a reversed tapered shape such that the upper aperture diameter is smaller than the lower aperture diameter, or to be formed in an overhang shape such that the upper aperture is extremely small. The reversed tapered shape and the overhang shape make it difficult to form a metal film by sputtering and to fill the hole with metal by plating for conductive connection between wirings. The preferable shape of the contact hole for the through electrode is a forward tapered shape such that the upper aperture is larger than the lower aperture.
Moreover, it is concerned that the negative photosensitive resin composition reaches a limit of resolution in accordance with the pattern miniaturization expected to further progress in future. That is, the negative photosensitive resin composition may cause pattern deterioration such as undissolved residues and a scum in the pattern bottom and a footing profile in the pattern on the substrate, e.g. when a coating film formed of the photosensitive resin composition on the substrate is thick. These scum and footing profile are likely to cause disconnection or interruption of an electric circuit and wiring during the rewiring process, so that it is necessary to inhibit generation of such problems. However, it cannot be denied that these scum and footing profile are difficult to be resolved since the miniaturization further progresses in the negative photosensitive resin composition.
On the other hand, the negative photosensitive resin composition capable of forming a fine pattern to be used for the rewiring process and useful for a top coat to protect electric and electronic parts occasionally covers a Cu wiring that has been previously processed on a substrate or an Al electrode on a substrate. In addition, the substrate provided with a wiring and an electrode includes an insulator substrate such as SiN, which needs to be widely covered. However, adhesion between such a substrate and a coating layer formed of the negative photosensitive resin composition is still insufficient, so that there often occurs a problem in which the coating layer of the negative photosensitive resin composition is delaminated from the substrate.
In addition, an organic solvent is commonly used as a developer in patterning with the negative photosensitive resin composition useful for a top coat to protect electric and electronic parts. In this case, an exposed part becomes insoluble in the organic solvent developer by a crosslinking reaction or the like, while an unexposed part is readily soluble in the organic solvent developer, providing a pattern.
However, there is an idea that the organic solvent development is not desirable in view of the disposal of waste liquid after development, load to an environment, and so forth. Moreover, the organic solvent developer is expensive. Thus, development with an aqueous alkaline solution such as a 2.38% tetramethylammonium hydroxide (TMAH) aqueous solution, which is inexpensive and widely used in lithography patterning, is preferred.
In the development with an aqueous alkaline solution of a 2.38% tetramethylammonium hydroxide (TMAH) aqueous solution, some negative photosensitive resin compositions used in recent years have small difference in solubility between an exposed part and an unexposed part with respect to the developer. In other words, a so-called dissolution contrast therebetween is sometimes small. When the dissolution contrast is small, it cannot be always expected to form a good pattern satisfying a demand of a fine pattern. Moreover, when the dissolution contrast is small, there is fear that a pattern cannot be formed on a substrate accurately according to a mask used for transferring and forming a pattern by exposure. Therefore, the photosensitive resin composition requires dissolution contrast as high as possible, i.e., improvement of resolution in use of an aqueous alkaline developer.
Accordingly, the photosensitive composition is desired to be capable of forming a fine pattern in the rewiring technology with the trends to higher density and higher integration of chips and to be useful for a top coat to protect electric and electronic parts as well as to have dramatically improved adhesiveness to a substrate. Moreover, it is desired that the contact hole for forming a through electrode connecting a metal wiring has a forward tapered shape. Furthermore, wanted is prompt building up of the system in which patterning is possible by a widely used alkaline developer such as a 2.38% TMAH aqueous solution, further improvement of resolution can be expected, and a scum and a footing profile are not generated in the pattern bottom.